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New Analytical Tools to Interrogate Inositol Pyrophosphate SignalingHarmel, Robert Klaus 26 June 2020 (has links)
Inositolpyrophosphate (PP-InsPs) sind eine wichtige Gruppe eukaryotischer Botenstoffe, die mit verschiedenen Prozessen wie Apoptose, Phosphathomeostase und Insulinsignalkaskaden verknüpft sind. Trotz ihrer Entdeckung vor mehr als 20 Jahren bleibt es eine Herausforderung, die Signalmechanismen dieser Moleküle zu verstehen. Ursachen dafür sind der limitierte Zugang zu synthetischen PP-InsPs und ein Mangel an allgemein zugänglichen analytischen Methoden. Daher wurden in dieser Arbeit chemische und analytische Verfahren entwickelt, um unser Verständnis von diesen Molekülen sowohl auf ein biochemischer als auch auf zelluläre Ebene zu verbessern.
Um der Knappheit an synthetischen PP-InsPs entgegen zu wirken, wurde eine hocheffiziente chemoenzymatische Synthese entwickelt, bei der mehr als 100 mg aller wesentlichen PP-InsPs aus Säugern hergestellt werden konnten. Parallel wurde ein neues analytisches Werkzeug entwickelt, dass Konzentrationen von PP-InsPs in komplexen Proben quantifizieren konnte. Mittels Enzymkatalyse konnten 13C-markiertes myo-inositol und 13C-markierte PP-InsPs hergestellt werden und niedrige Konzentrationen mit nuklearer Magnetresonanzspektroskopie detektiert werden. In vitro waren diese Verbindungen sehr nützlich, um PP-InsP Kinasen von Pflanzen und Säugern zu charakterisieren. Endogene Konzentrationen von PP-InsPs konnten durch metabolisches Markieren mit 13C-markiertem myo-inositol in humanen Zelllinien quantifiziert werden. Letztendlich wurde mittels eines neuen entwickelten proteomischen Ansatzes endogene Proteinpyrophosphorilierung, eine von PP-InsP eingebaute posttranslationale Proteinmodifikation, in menschlichen Zelllinien zum ersten Mal nachgewiesen.
Zusammenfassend haben die aufgelisteten chemischen und analytischen Werkzeuge ein hohes Potenzial unser Verständnis der Signalmechanismen hinter den diversen Phänotypen der PP-InsPs zu stärken und Forschungsarbeit in dieser Richtung zu beschleunigen. / Inositol pyrophosphates (PP-InsPs) are an important group of second messengers that intersect with a wide range of processes in eukaryotic cells including phosphate homeostasis, insulin signaling and apoptosis. Despite their discovery more than two decades ago, elucidating the underlying signaling mechanisms remains a significant challenge. Therefore, a new set of chemical and analytical methods was developed here to improve our understanding of these intriguing molecules on the biochemical and cellular level.
To overcome the shortage of synthetic PP-InsPs, a highly efficient and scalable chemoenzymatic approach was designed and the major mammalian PP-InsPs could be obtained in hundreds of milligram quantities and in high purity. In parallel, a new analytical tool was developed to quantify levels of PP-InsPs in complex samples. Chemoenzymatic access to 13C-labeled myo-inositol and 13C-labeled PP-InsPs enabled the detection of low concentrations of PP-InsPs using nuclear magnetic resonance spectroscopy. In vitro, these compounds were of great use for the biochemical characterization of PP-InsPs kinases from mammals and plants. Endogenous pools of PP-InsPs from human cell lines were identified and quantified by metabolic labeling with 13C-labeled myo-inositol. Finally, a new proteomics workflow towards the detection of protein pyrophosphorylation, a posttranslational modification mediated by PP-InsPs, using mass spectrometry was optimized and endogenously modified mammalian proteins could be identified for the first time and with high confidence.
Taken together, the chemical and analytical tools presented here have great potential to accelerate the understanding of PP-InsP signaling and metabolism. Access to large amounts of PP-InsPs together with a reliable quantification method and the detection of endogenous protein pyrophosphorylation sites will be essential to unravel the signaling mechanisms underlying the diverse phenotypes associated with these metabolites.
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SYNTHESIS AND VISCOELASTIC PROPERTIES OF GELS OBTAINED FROM LINEAR AND BRANCHED POLYMERSDebnath, Dibyendu, Debnath 24 May 2018 (has links)
No description available.
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SYNTHESIS AND VISCOELASTIC PROPERTIES OF GELS OBTAINED FROM LINEAR AND BRANCHED POLYMERSDebnath, Dibyendu 24 May 2018 (has links)
No description available.
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NMR-Based Metabolomics for the Identification of Biomarkers of DiseaseBotello Marabotto, Marina Dolores 03 November 2024 (has links)
[ES] La tesis doctoral titulada "NMR-based metabolomics for the identification of biomarkers of disease" explora el potencial de la metabolómica mediante espectroscopía de resonancia magnética nuclear (RMN) para la identificación de biomarcadores de enfermedades, permitiendo un diagnóstico temprano y no invasivo, así como el seguimiento de pacientes. El estudio se centra en cuatro enfermedades: Alzheimer, glaucoma, aterosclerosis y vulnerabilidad de placa, y fibrosis pulmonar tras neumonía por COVID-19.
En la introducción, se describe el proceso de análisis metabolómico para la identificación de biomarcadores y las principales plataformas y herramientas estadísticas utilizadas en el análisis mediante RMN. Se destacan las características fisiopatológicas de las enfermedades estudiadas, las formas actuales de diagnóstico y la necesidad de nuevos marcadores.
El primer capítulo aborda la identificación de biomarcadores para el Alzheimer y la progresión de deterioro cognitivo leve (MCI) a Alzheimer mediante análisis de suero. Se desarrollaron modelos de clasificación que discriminaron entre Alzheimer, MCI y controles sanos. La investigación encontró que ciertos metabolitos, como lisina, piruvato y colina, presentan concentraciones distintas según la evolución del MCI.
El segundo capítulo estudia las diferencias metabolómicas entre MCI y controles mediante análisis de plasma, combinando RMN y marcadores de peroxidación lipídica detectados con UPLC-MS/MS. La combinación de ambas técnicas mejoró la identificación de biomarcadores, destacando metabolitos como isoleucina, valina y glutamato.
El tercer capítulo analiza lágrimas de pacientes con glaucoma primario de ángulo abierto (POAG) para identificar biomarcadores en un medio mínimamente invasivo. Se identificaron metabolitos como taurina, glicina y glucosa como potenciales biomarcadores.
En el cuarto capítulo se estudian placas de ateroma y suero de pacientes con estenosis de carótida para identificar biomarcadores de vulnerabilidad de placa. En placa, se identificaron mio-inositol y glutamato como potenciales biomarcadores. En suero, se destacaron treonina, histamina y ácidos grasos insaturados.
El quinto capítulo se enfoca en pacientes que desarrollaron fibrosis pulmonar tras neumonía por COVID-19, identificando biomarcadores en suero que permiten predecir la fibrosis, destacando glucosa, valina y ácidos grasos.
Finalmente, se presenta la discusión y las conclusiones generales, subrayando la relevancia de la metabolómica mediante RMN para identificar biomarcadores tempranos y no invasivos, lo que podría cubrir una necesidad crítica en la medicina actual. / [CA] La tesi doctoral titulada "Metabolòmica basada en RMN per a la identificació de biomarcadors de malaltia" explora el potencial de la metabolòmica mitjançant espectroscòpia de ressonància magnètica nuclear (RMN) per a la identificació de biomarcadors de malalties, permetent un diagnòstic precoç i no invasiu, així com el seguiment de pacients. L'estudi se centra en quatre malalties: Alzheimer, glaucoma, aterosclerosi i vulnerabilitat de placa, i fibrosi pulmonar després de pneumònia per COVID-19.
A la introducció, es descriu el procés d'anàlisi metabolòmic per a la identificació de biomarcadors i les principals plataformes i eines estadístiques utilitzades en l'anàlisi mitjançant RMN. Es destaquen les característiques fisiopatològiques de les malalties estudiades, les formes actuals de diagnòstic i la necessitat de nous marcadors.
El primer capítol tracta sobre la identificació de biomarcadors per a l'Alzheimer i la progressió de deteriorament cognitiu lleu (MCI) a Alzheimer mitjançant anàlisi de sèrum. Es van desenvolupar models de classificació que van discriminar entre Alzheimer, MCI i controls sans. La investigació va trobar que certs metabòlits, com lisina, piruvat i colina, presenten concentracions diferents segons l'evolució del MCI.
El segon capítol estudia les diferències metabolòmiques entre MCI i controls mitjançant anàlisi de plasma, combinant RMN i marcadors de peroxidació lipídica detectats amb UPLC-MS/MS. La combinació d'ambdues tècniques va millorar la identificació de biomarcadors, destacant metabòlits com isoleucina, valina i glutamat.
El tercer capítol analitza llàgrimes de pacients amb glaucoma primari d'angle obert (POAG) per a identificar biomarcadors en un medi mínimament invasiu. Es van identificar metabòlits com taurina, glicina i glucosa com a potencials biomarcadors.
En el quart capítol s'estudien plaques d'ateroma i sèrum de pacients amb estenosi de caròtida per a identificar biomarcadors de vulnerabilitat de placa. En placa, es van identificar mio-inositol i glutamat com a potencials biomarcadors. En sèrum, es van destacar treonina, histamina i àcids grassos insaturats.
El cinqué capítol se centra en pacients que van desenvolupar fibrosi pulmonar després de pneumònia per COVID-19, identificant biomarcadors en sèrum que permeten predir la fibrosi, destacant glucosa, valina i àcids grassos.
Finalment, es presenten les conclusions generals, subratllant la rellevància de la metabolòmica mitjançant RMN per a identificar biomarcadors precoços i no invasius, la qual cosa podria cobrir una necessitat crítica en la medicina actual. / [EN] The doctoral thesis titled "NMR-based metabolomics for the identification of biomarkers of disease" explores the potential of metabolomics through nuclear magnetic resonance (NMR) spectroscopy for the identification of disease biomarkers, enabling early and non-invasive diagnosis, as well as patient monitoring. The study focuses on four diseases: Alzheimer's, glaucoma, atherosclerosis and plaque vulnerability, and pulmonary fibrosis after COVID-19 pneumonia.
The introduction describes the metabolomic analysis process for biomarker identification and the main platforms and statistical tools used in NMR-based analysis. The study highlights the pathophysiological characteristics of the diseases studied, current diagnostic methods, and the need for new biomarkers.
The first chapter addresses the identification of biomarkers for Alzheimer's disease and the progression of mild cognitive impairment (MCI) to Alzheimer's using serum analysis. Classification models were developed to distinguish between Alzheimer's, MCI, and healthy controls. The research found that certain metabolites, such as lysine, pyruvate, and choline, show different concentrations depending on the evolution of MCI.
The second chapter studies metabolomic differences between MCI and controls using plasma analysis, combining NMR and lipid peroxidation markers detected by UPLC-MS/MS. The combination of both techniques improved biomarker identification, highlighting metabolites such as isoleucine, valine, and glutamate.
The third chapter analyzes tears from patients with primary open-angle glaucoma (POAG) to identify biomarkers in a minimally invasive medium. Metabolites such as taurine, glycine, and glucose were identified as potential biomarkers.
In the fourth chapter, atheroma plaques and serum from patients with carotid stenosis were studied to identify biomarkers of plaque vulnerability. In plaques, myo-inositol and glutamate were identified as potential biomarkers. In serum, threonine, histamine, and unsaturated fatty acids were highlighted.
The fifth chapter focuses on patients who developed pulmonary fibrosis after COVID-19 pneumonia, identifying serum biomarkers that can predict fibrosis, with glucose, valine, and fatty acids being prominent.
Finally, the general discussion and conclusions are presented, emphasizing the relevance of NMR-based metabolomics in identifying early and non-invasive biomarkers, potentially addressing a critical need in modern medicine. / Botello Marabotto, MD. (2024). NMR-Based Metabolomics for the Identification of Biomarkers of Disease [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/211472
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Die Aktivierung von reaktionsträgen kleinen Molekülen an koordinativ ungesättigten Beta-Diketiminato-NickelkomplexenHolze, Patrick 06 September 2016 (has links)
Kleine Moleküle wie Treibhausgase, aber auch Distickstoff und Disauerstoff stehen im Fokus der chemischen Forschung. Solche Moleküle sind durch ihr Vorkommen in der Atmosphäre ubiquitär vorhanden, preiswert und könnten als Synthesebausteine für die Darstellung von komplexeren Molekülen verwendet werden. In dieser Arbeit wurde die Reaktion koordinativ ungesättigter Diketiminato-Nickelkomplexe ([LNi] Komplexe) mit kleinen Molekülen untersucht. Zunächst wurden die Mechanismen der N2-Aktivierung durch reduzierte [LtBuNiI]- und [LMe6NiI] Komplexe miteinander verglichen. Dabei konnte das distickstoffaktivierende Schlüsselintermediat identifiziert und strukturell charakterisiert werden. Weiter wurden die N2-Komplexe [(LtBuNiI)( 1 1 N2)] bzw. K2[(LtBuNiI)( 1 1 N2)], die Vorläufer für [LNiI]- und [LNi0]– Komplexfragmente darstellen, hinsichtlich ihrer Potentials zur Aktivierung der reaktionsträgen Treibhausgase SF6 und NF3 untersucht. Über Reaktionen von Übergangsmetallkomplexen mit NF3 war bis dahin noch nicht berichtet worden; zur Umsetzung von SF6 existierten wenige Publikationen, in denen aber sehr viele mechanistische Fragen offengeblieben sind. Die Mechanismen der SF6- und NF3-Aktivierung wurden durch Kombination einer Vielzahl von ex- und in situ Analysen beleuchtet. Im Falle der SF6 Aktivierung gelang es zudem, ein Nickel(I)-Intermediat zu isolieren. Ein Produkt beider Systeme war der Fluorido-Nickel(II)-Komplex [LtBuNiIIF], dessen Reaktionsverhalten ebenfalls studiert wurde. Doch nicht nur Komplexe mit Nickelatomen in niedrigen Oxidationsstufen erwiesen sich für die Aktivierung kleiner Moleküle geeignet, sondern auch kationische [LtBuNiII(D)]+-Komplexe. Diese Nickel(II)-Komplexe reagierten mit fluorierten Molekülen, N2O sowie O2, was bemerkenswert ist, da Nickel(II)-Komplexe üblicherweise inert gegenüber O2 sind. Im Zuge der O2-Studien wurde ein metastabiler Oranoperoxidkomplex isoliert und strukturell charakterisiert, was beispiellos in der Literatur ist. / Current research focuses on the activation of small molecules like greenhouse gases, thermodynamically stable molecules like N2 and kinetically stabilized molecules like O2, which are all abundant in the atmosphere. Thus, it appears to be alluring to use them as cheap and readily available building blocks for the synthesis of value-added compounds. This dissertation deals with the reaction of low-coordinate diketiminate nickel complexes [LNi] and such small molecules. Initially, the mechanisms of the dinitrogen activation by reduced [LtBuNiI] and [LMe6NiI] complexes were studied. As a result, the key intermediate [(LtBuNiI)x(3 Br)xKx] (x > 1) was identified and structurally characterized. Subsequently, the nickel complexes [(LtBuNiI)( 1 1 N2)] and K2[(LtBuNiI)( 1 1 N2)], which represent sources for [LtBuNiI] and [LtBuNi0]– moieties, were applied to the activation of the inert, but very efficient greenhouse gases SF6 and NF3. Prior to these investigations, no transition metal complex had been reported to react with NF3. Publications dealing with the conversion of SF6 had been scarce, too, while at same time, the mechanisms involving its activation had been speculative. The mechanisms of the NF3 and SF6 activation reactions were deduced combining numerous ex-situ and in situ analytical methods. In case of the SF6 activation, even an intermediate could be isolated. In both systems, the nickel fluoride complex [LtBuNiIIF] was formed and its reaction behaviour was also studied. Furthermore, not only [LtBuNiI]- and [LtBuNi0]– moieties proved to be reactive towards small molecules, but also cationic [LtBuNiII(D)]+ complexes, which were specifically developed for this purpose. The reactions of [LtBuNiII(D)]+ complexes with fluorinated molecules (e. g. PhF, NF3), O2 and N2O were studied. In course of the O2 activation, a metastable organoperoxide complex was isolated and structurally characterized, which is unparalleled in the literature.
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Structural and functional characterisation of the collagen binding domain of fibronectinMillard, Christopher John January 2007 (has links)
Fibronectin is an extracellular multidomain glycoprotein that directs and regulates a variety of cell processes such as proliferation, development, haemostasis, embryogenesis, and wound healing. As a major component of blood, fibronectin exists as a soluble disulphide linked dimer, but it can also be incorporated into an insoluble cross-linked fibrillar network to form a major component of the extracellular matrix. Fibronectin is composed of an extended chain of module repeats termed Fn1, Fn2, and Fn3 that bind to a wide range of transmembrane receptors and extracellular matrix components, including collagen. The gelatin binding domain of fibronectin was first isolated as a 45kDa proteolytic fragment and has since been found to be composed of six modules: 6Fn1-1Fn2-2Fn2-7Fn1-8Fn1-9Fn1 (in this notation nFX represents the nth type X module in the native protein). This domain has been reported to bind to both collagen and denatured collagen (gelatin), but with 10-100 times higher affinity to the latter; it can be purified to homogeneity on a gelatin affinity column. In the work presented here, fragments of the gelatin binding domain are expressed in P. pastoris, purified to homogeneity, and investigated at the molecular level. Through a dissection approach, surface plasmon resonance (SPR) is used to characterise the recombinantly produced protein, to accumulate more information about the function of the full domain. NMR is used to assess the folding of the protein fragments at atomic resolution. In particular, the secondary structure of 8Fn1-9Fn1 is mapped using inter-strand NOEs, which suggests that the construct takes the fold of a pair of typical Fn1 modules. Gelatin affinity chromatography is used to confirm that both Fn1 and Fn2 modules contribute to gelatin binding, possibly in two clusters (1Fn2-2Fn2 and 8Fn1-9Fn1). The 7Fn1 module may perform a structural role in linking together these two interaction sites, in the same way as suggested for 6Fn1, which is thought to act in a structural manner to enhance the binding of 1Fn2-2Fn2 to gelatin. Three carbohydrate moieties are found on this domain, one on 2Fn2 and two on 8Fn1. Here, by means of expressing different protein length fragments, and by site directed mutagenesis, the role of each sugar chain is investigated independently. The sugar chain on 2Fn2 does not appear to promote binding to collagen, nor does the first sugar chain on 8Fn1 (N-linked to N497), implying another role for these sugars such as protection from proteolysis. However, the presence of at least a single GlcNAc sugar residue on the second sugar chain site on 8Fn1 (N- linked to N511) is essential for full affinity binding to collagen. Direct binding of the 8Fn1-9Fn1 module pair to collagen is assessed with a short collagen peptide and the binding is monitored by NMR. The peptide appears to bind, predominantly to the final strand of 8Fn1, the first β- strand of 9Fn1, and the linker between the two modules, with μM affinity. A model for bound peptide is proposed. The highly conserved amino acid motif Ile-Gly-Asp (IGD) is found on four of the nine N-terminal Fn1 modules of fibronectin. Tetrapeptides containing the IGD were demonstrated to promote the migration of fibroblast cells into a native collagen matrix. Two of these “bioactive” IGD motifs are found within the gelatin binding domain, one on 7Fn1 and one on 9Fn1. In this study, the motif in the 8Fn1-9Fn1 module pair is shown to be located in a tightly constrained loop within 9Fn1. By site directed mutagenesis, the IGD motifs of 7Fn1 and 9Fn1 are subjected to single amino acid substitutions, and their ability to stimulate cell migration assessed in our assay. By NMR, the fold of the IGD mutant proteins is found to be unaffected by the mutation with respect to the wild type, with the exception of small perturbations around the substitution site. While the wild type module is able to stimulate fibroblast migration, the mutant proteins show reduced or negligible bioactivity. The larger fragments show far more potency in stimulating fibroblast migration, with 8Fn1-9Fn1 (one IGD motif) 104 times more potent than the IGD peptide, and the full gelatin binding domain (two IGD motifs) 106 times more potent than the 8Fn1-9Fn1. Potential mechanisms for this enormous enhancement of the IGD potency in different contexts are discussed.
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Coherent transfer between electron and nuclear spin qubits and their decoherence propertiesBrown, Richard Matthew January 2012 (has links)
Conventional computing faces a huge technical challenge as traditional transistors will soon reach their size limitations. This will halt progress in reaching faster processing speeds and to overcome this problem, require an entirely new approach. Quantum computing (QC) is a natural solution offering a route to miniaturisation by, for example, storing information in electron or nuclear spin states, whilst harnessing the power of quantum physics to perform certain calculations exponentially faster than its classical counterpart. However, QCs face many difficulties, such as, protecting the quantum-bit (qubit) from the environment and its irreversible loss through the process of decoherence. Hybrid systems provide a route to harnessing the benefits of multiple degrees of freedom through the coherent transfer of quantum information between them. In this thesis I show coherent qubit transfer between electron and nuclear spin states in a <sup>15</sup>N@C<sub>60</sub> molecular system (comprising a nitrogen atom encapsulated in a carbon cage) and a solid state system, using phosphorous donors in silicon (Si:P). The propagation uses a series of resonant mi- crowave and radiofrequency pulses and is shown with a two-way fidelity of around 90% for an arbitrary qubit state. The transfer allows quantum information to be held in the nuclear spin for up to 3 orders of magnitude longer than in the electron spin, producing a <sup>15</sup>N@C<sub>60</sub> and Si:P ‘quantum memory’ of up to 130 ms and 1.75 s, respectively. I show electron and nuclear spin relaxation (T<sub>1</sub>), in both systems, is dominated by a two-phonon process resonant with an excited state, with a constant electron/nuclear T<sub>1</sub> ratio. The thesis further investigates the decoherence and relaxation properties of metal atoms encapsulated in a carbon cage, termed metallofullerenes, discovering that exceptionally long electron spin decoherence times are possible, such that these can be considered a viable QC candidate.
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Hybrid ferrocene-based systemsKelly, Michael Jon January 2014 (has links)
This thesis explores the capacity of sterically and electronically unsaturated boranes to bind substrates of biological and environmental interest, and transduce such binding events into a photo-physical and/or electrochemical response, hence reporting the presence of these substrates. Chapter three details the synthesis of a range of novel ferrocenyl boranes featuring either a proximal hydrogen-bond donor or a second Lewis acidic centre. These novel boranes were shown to be competent at binding both cyanide and fluoride anions, with the role played by a proximal hydrogen-bond donor or a second Lewis acidic centre in anion binding investigated by both NMR and crystallographic studies. Chapter four reports the synthesis of novel pyridinyl and related boronic esters, as well as unexpected mixed alkenyl/aryl boranes. The capacity of both types of system to bind fluoride or cyanide anions in solution was investigated by UV-Vis and NMR studies. The photo-physical responses to these anions were also probed, leading to the establishment of both switch-on and switch-off fluorescent responses. Chapter five extends the knowledge derived from selective anion receptor design and combines this with recent developments in the field of frustrated Lewis pairs (FLPs) to activate, bind and report the presence of nitrous oxide (N<sub>2</sub>O) molecule. Thus, the syntheses of novel, highly Lewis acidic ferrocenyl boranes that incorporate a high degree of steric loading around the boron centre are reported. The electrochemical and photo-physical response of an FLP system to the presence of N<sub>2</sub>O was investigated leading to the development of a novel N<sub>2</sub>O reporting system.
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Sulfonamide supported catalysts for the ring opening polymerisation of cyclic estersSchwarz, Andrew Douglas January 2010 (has links)
This Thesis describes the synthesis and characterisation of sulfonamide supported titanium, zirconium and aluminium complexes and their use as ring opening polymerisation catalysts for ε-caprolactone and rac-lactide. Chapter 1 introduces polyester use, development and characterisation in general. Metal catalysed ring opening polymerisation of cyclic esters is considered in a literature review of the field. Titanium, zirconium and aluminium complexes supported by polydentate sulfonamide ligands are also discussed. Chapter 2 describes the synthesis and characterisation of new sulfonamide supported titanium amide, isopropoxide and zirconium isopropoxide complexes. Their application as catalysts for the ring opening polymerisation of ε-caprolactone and rac-lactide is discussed and compared with known zirconium isopropoxide complexes supported by bis(phenolate) amine ligands. Chapter 3 describes the synthesis and characterisation of Cs symmetric titanium amide and alkoxide complexes supported by dianionic, tri- and tetradentate sulfonamide ligands. Zirconium alkyl and amide complexes supported by C3- symmetric trianionic ‘tren’ type ligands bearing three different sulfonamide groups are also presented. The application of these complexes for the ring opening polymerisation of ε-caprolactone and rac-lactide is described and compared with the complexes presented in Chapter 2. Chapter 4 provides an overview of the synthesis and characterisation of aluminium alkoxide and alkyl complexes supported by dianionic, tri- and tetradentate sulfonamide ligands. Solution state behaviour and solid state structures are presented and discussed. An assessment of these complexes for the ring opening polymerisation of rac-lactide is presented. Chapter 5 presents full experimental procedures and characterisation data for the new complexes reported. CD Appendix contains .cif files for all new crystallographically characterised complexes described, and additional polymerisation graphs.
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Chemistry of Cyanoform (Tricyanomethane); and Rearrangement of 1H-1,2,3-Triazoles to the Corresponding 2H-Isomers / Die Chemie des Cyanoforms (Tricyanomethan) und Umlagerung von 1H-1,2,3-Triazolen in die entsprechenden 2H-IsomereChityala, Madhu 28 March 2017 (has links) (PDF)
Cyanoform (tricyanomethane) is one of the strongest carbon-based organic acids reported in text books of organic chemistry, which has evaded synthesis and isolation in its free state, since 120 years. In this dissertation, the acid-free synthesis of cyanoform by an absolutely new approach has been discussed. Generation of the elusive molecule, cyanoform from the photolysis and thermolysis of 2-(azidomethylidene)malononitrile, has been confirmed at very low temperatures by 1H NMR, 13C NMR, 15N NMR, and the relevant 2D NMR spectroscopic techniques. Moreover, it has been proved that cyanoform is relatively stable, but can be detected only below –85 oC, and not at high temperatures (at –45 oC, as has been reported in literature), because of a rapid equilibration with an another species. Furthermore, the chemistry of cyanoform in the ring enlargement reactions with various highly strained epoxides, azirines, and aziridines, via the highly reactive dicyanoketenimine intermediate, as well as its Michael addition reactions with different α,β-unsaturated carbonyl compounds has been well explored.
In addition, the synthesis of N1-substituted 1,2,3-triazoles and study of their rearrangement to the corresponding N2-substituted 1,2,3-triazoles, under thermal and nucleophile-catalyzed reaction conditions, has been well investigated. / Cyanoform (Tricyanomethan) ist eine der stärksten in der Literatur beschriebenen organischen Kohlenstoffsäuren, welche sich seit 120 Jahren einer erfolgreichen Synthese und Isolierung entzogen hat. In dieser Arbeit wird die säurefreie Synthese des Cyanoforms mittels eines neuartigen Ansatzes diskutiert. Die Bildung des schwer fassbaren Moleküls durch Photolyse und Thermolyse von 2 (Azidomethyliden)malonitril ist bei tiefen Temperaturen durch 1H-NMR, 13C-NMR, 15N-NMR und relevante 2D-NMR-Methoden bestätigt worden. Es konnte bewiesen werden, dass Cyanoform relative stabil ist, aber erst unterhalb von –85 °C detektierbar ist und nicht bereits bei hӧherer Temperature (bei –45 °C, wie es in der Literatur beschrieben wurde) bedingt durch die rasche Äquilibrierung mit einer weiteren Species. Des Weiteren wurde die Reaktivität von Cyanoform in Ringerweiterungsreaktionen mit verschiedenen, stark gespannten Epoxiden, Azirinen und Aziridinen untersucht, wobei das hoch reaktive Dicyanoketenimin-Intermediat durchlaufen wird. Auch die Michael-Addition an α,β ungesättigte Carbonylverbindungen wurde ausführlich untersucht.
Zusätzlich wurde die Synthese N1 substituierter 1,2,3-Triazole und deren Umlagerung in N2 substituierte 1,2,3-Triazole unter thermischen und nucleophil-katalysierten Bedingungen erforscht.
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